In the 3GPP (3rd Generation Partnership Project), the standard of EUTRA (Evolved Universal Terrestrial Radio Access; hereinafter referred to as “EUTRA”) is already established, and a study on a radio access scheme (Advanced EUTRA; hereinafter referred to as “A-EUTRA”), which is an evolved EUTRA, is being started.
<EUTRA SRS>
In E-UTRA, for example, a sounding reference signal (SRS) is already specified in order for a base station apparatus to measure an uplink channel quality. A mobile station apparatus transmits the sounding reference signal through the use of a radio resource that is set in advance by the base station apparatus. To the mobile station apparatus, a radio resource for periodically transmitting the sounding reference signal is allocated or a radio resource for transmitting the sounding reference signal only once is allocated. The sounding reference signal is transmitted only in a periodic subframe (referred to as an SRS subframe) of a physical uplink that is set in advance by a base station apparatus. Moreover, the sounding reference signal is transmitted using the last SC-FDMA (Single Carrier-Frequency Division Multiple Access) symbol of an uplink subframe.
<EUTRA PUCCH>
In E-UTRA, for example, a physical uplink control channel (PUCCH) is already specified in order for a mobile station apparatus to transmit a scheduling request. The scheduling request means that a mobile station apparatus requires a radio resource allocation of a physical uplink shared channel (PUSCH), of a base station apparatus. When making the scheduling request, a mobile station apparatus transmits a physical uplink control channel signal through the use of a periodic radio resource that is set in advance by a base station apparatus. When not making the scheduling request, a mobile station apparatus does not transmit a signal for the scheduling request even if a radio resource has been allocated.
In E-UTRA, there are two types of formats of the physical uplink control channel signal which are used for transmitting a scheduling request (hereinafter, referred to as a first format and a second format). The first format is a format, in which a radio resource in a time domain to which a sounding reference signal may be allocated, i.e., an SC-FDMA symbol to which a sounding reference signal may be allocated, is used for transmission of a scheduling request, while the second format is a format, in which a radio resource in a time domain to which a sounding reference signal may be allocated, i.e., an SC-FDMA symbol to which a sounding reference signal may be allocated, is not used for transmission of a scheduling request.
<Simultaneous Generation of EUTRA SRS and PUCCH>
In E-UTRA, a mode in which a mobile station apparatus can simultaneously transmit a sounding reference signal and a physical uplink control channel signal, and a mode in which a mobile station apparatus cannot transmit a sounding reference signal when the mobile station apparatus transmits a physical uplink control channel signal, are switched and used by a base station apparatus. When a sounding reference signal and a physical uplink control channel signal are simultaneously transmitted in the same subframe, the second format is used as the format for the physical uplink control channel signal.
More specifically, in the sounding reference signal subframe, control information indicating whether, as the format for the physical uplink control channel signal, the first format is used or the second format is used is broadcasted from a base station apparatus to mobile station apparatuses. When in a sounding reference signal subframe, the control information indicating that the first format is used as the format of a physical uplink control channel signal is provided by a base station apparatus, a mobile station apparatus transmits a physical uplink control channel signal by using the first format in the sounding reference signal subframe, and furthermore, when a physical uplink control channel signal is transmitted in the sounding reference signal subframe to which the radio resource for the sounding reference signal has been allocated, the mobile station apparatus transmits only a physical uplink control channel signal without transmitting the sounding reference signal.
When in a sounding reference signal subframe, the control information indicating that the second format is used as the format of a physical uplink control channel signal is provided by a base station apparatus, a mobile station apparatus transmits a physical uplink control channel signal using the second format in the sounding reference signal subframe, and furthermore, when a physical uplink control channel signal transmitted in the sounding reference signal subframe to which the radio resource for the sounding reference signal has been allocated, the mobile station apparatus simultaneously transmits the sounding reference signal and the physical uplink control channel signal.
<Component Carrier Aggregation>
In contrast, in A-EUTRA, supporting a frequency band wider than in EUTRA and securing the compatibility with EUTRA are being examined. Therefore, in A-EUTRA, a technique (may be referred to as also spectrum aggregation or carrier aggregation) is being examined, in which a base station apparatus carries out communications using a system bandwidth composed of a plurality of component frequency bands, with the frequency band of EUTRA as one unit (one component frequency band) (it should be noted that, the component frequency band may be referred to as also a carrier component or a component carrier (see non-Patent Document 1). In this technique, a base station apparatus carries out communications with an EUTRA-compliant mobile station apparatus by using either one component frequency band in an uplink and in a downlink, respectively, and carries out communications with an A-EUTRA-compliant mobile station apparatus by using one or more component frequency bands in an uplink and in a downlink, respectively.